(1) Field of the Invention
The present invention relates to a CCD (charge coupled device) camera system which is capable of a multi-media response. More specifically, the CCD camera system has two CCDs which have an aspect ratio corresponding to an international standard, to S thereby avoid the necessity of frequency conversion when interfacing with a digital signal processor. The CCDs also have complimentary stripe patterns to improve the horizontal resolution of the brightness signals and the vertical resolution of the color signals.
(2) Description of the Prior Art
The conventional CCD camera system will be described with reference to the attached drawings.
FIG. 1 is a block diagram showing the constitution of the conventional CCD camera system.
As shown in FIG. 1, the conventional CCD camera system includes:
a lens part 10 for focusing the optical signals of an object;
a CCD 11 for converting the imaged optical signals into electrical signals, when the optical signals from the lens part 10 is imaged;
a sampling/holding device 12 for carrying out a sampling/holding function, so as to remove unnecessary signals such as noise and the like from among the output video signals of the CCD 11;
an analog-digital converter 13 for converting the output analog video signals of the sampling/holding device 12 into digital video signals, so as to carry out a digital signal processing;
a first line memory 14 for storing the one period (1H) delayed output signals of the analog-digital converter 13;
a second line memory 15 for storing the one period (1H) delayed signals of the first line memory 14;
a brightness signal generator 16 for generating brightness signals Y by using the stored signals of the first line memory 14; and
a color signal generator 17 for generating color signals Cr and Cb by utilizing an internal color difference signal matrix and by receiving the output signals of the analog-digital converter 13 and the stored signals of the first and second line memories 14 and 15.
The conventional CCD camera constituted as described above operates in the following manner.
In processing color signals by using a single plate type CCD, if the color is to be restored, independent color components have to be provided rather than just color components from a tingle pixel. Recently, among methods using a single plate CCD, a complementary filtering method (a filtering method using the color components of magenta Mg, cyan Cy, yellow Ye, green G) has been used because of its superior spectrum sensitivity characteristics.
The color filter array pattern of the single plate type CCD is constituted such that, horizontally, there are repeatedly arranged lines S1 having components xe2x80x9cmagenta+cyanxe2x80x9d and xe2x80x9cgreen+cyanxe2x80x9d, and lines S2 having components xe2x80x9cgreen+yellowxe2x80x9d and xe2x80x9cmagenta+yellowxe2x80x9d. Vertically, if it is assumed that the components xe2x80x9cmagenta+cyanxe2x80x9d and xe2x80x9cgreen+yellowxe2x80x9d are Nth line pixels, then the components xe2x80x9cgreen+cyanxe2x80x9d and xe2x80x9cmagenta+yellowxe2x80x9d are (Nxe2x88x921)th or (N+1)th line pixels.
The single plate CCD is further broken down vertically into odd fields and even fields, and the pixel components of the lines S1 and S2 are different according to their respective fields.
As described above, the color filter array of the CCD has a sequential structure for each pixel and for each line, and therefore, if the color signals of red R, green G and blue B are to be generated, horizontal and vertical interpolation processes have to be carried out by utilizing the adjacent pixels of the color filter array. Particularly, if the vertical interpolation is to be carried out, the two line memories 14 and 15 of FIG. 1 are used, so as to store the signals of the currently inputted video signals which are delayed by one period (1H) and which are delayed by two periods (2H). Then, based on the signals delayed by one period, an interpolation is carried out by using the currently inputted video signals and the signals delayed by two periods (2H).
In other words, as shown in FIG. 1, the output signals of the CCD 11 are quantized through the sampling/holding device 12 and through the analog-digital converter 13. The quantized signals of the CCD 11 come to have a simultaneity in three lines through the two line memories 14 and 15, with the result that color signals are generated through the horizontal and vertical interpolations.
This single plate type CCD signal processing method is effective in reducing costs. However, because both brightness signals and color signals are produced in the single plate type CCD, a single pixel is not capable of independently generating video signals. Rather, to generate video signals, it is necessary to interpolate different color information of horizontally and vertically adjacent pixels, respectively. Consequently, the resolution for the brightness signals and color signals is reduced, and the picture quality is lowered. As described above, in the conventional camera system, the signals are processed by using the CCD of a complementary pattern. However, this cannot satisfy the resolution of the CCIR 601 format which has 720 lateral pixels and 480 longitudinal pixels, which is the international resolution standard.
Further, the conventional CCD camera system is designed such that it can be applied to the existing analog signal processing system. Therefore, the aspect ratio of the CCD has been used for normal or a high band (H18). The normal type includes 250 thousand effective pixels and has a sampling frequency fs of 9.545 MHz. The high band type includes 380 thousand effective pixels and has a sampling frequency fs of 14.3 MHz.
The sampling frequency fs has no significance in an analog system. However, inasmuch as video signal processing is generally moving toward digital signal processing, the sampling frequency has become an important consideration and the lateral and longitudinal sizes of the video signals to be processed have been adapted to the international standard (lateral:longitudinal=4:3). That is, the frequency of the conventional CCD is incompatible with the international standard (fs: 13.5 MHz) which has been specified for digital video signals. Therefore; it is a disadvantage that a frequency conversion has to be carried out to achieve an interface between the conventional analog system and a system incorporating digital signal processing.
The present invention is intended to overcome the above described disadvantages of the conventional technique.
Therefore it is a first object of the present invention to provide a CCD camera system capable of a multi-media response, in which the CCD system is constructed by utilizing a CCD having an aspect ratio suitable to the international signal processing standard, i.e., a CCD having an effective pixel region compatible with the international standard, so that it is possible to even digitally process the image without performing a frequency conversion.
Further, the present invention is intended to overcome the problems of deterioration of the resolution of the brightness signals and the degradation of the picture quality of the color signals when using the conventional single plate type CCD of the complementary pattern.
Therefore, it is a second object of the present invention to provide a CCD camera system capable of a multi-media response having two CCDs which utilize the adjacent pixels having different color information and which therefore requires no horizontal and vertical interpolations. That is, a CCD having a striped pattern is formed to enable processing without using two line memories, and to enable the horizontal resolution of the brightness signals to attain the international standard (CCIR 601 format), thereby improving the vertical resolution of the color signals and improving the color regeneration.
In achieving the above objects, the CCD camera system capable of a multi-media response according to the present invention includes:
a prism means for splitting the focused optical signals of said lens;
part into a first beam and a second beam signals of the lens part in accordance with the frequency;
first and second CCDs for respectively converting imaged optical signals into electrical signals after the optical signals are split into two beams by the prism means, and having mutually different color filter arrays consisting of a complementary color stripe pattern and an effective number of pixels corresponding to the international standard;
first and second sampling/holding means for carrying out sampling and holding functions to remove unnecessary signals such as noises from the output video signals of the first and second CCDs;
first and second analog-digital converting means for converting the output analog video signals of the first and second sampling/holding means into digital signals for carrying out a digital signal processing; and
a CCD video signal processing means for receiving the output signals of the first and second analog-digital converting means to calculate the sum of and the difference between the two sets of signals so as to generate brightness signals and color signals.
The CCD video signal processing means includes:
a first arithmetic means for adding up respective output signals of the first and second analog-digital converting means;
a second arithmetic means for subtracting respective output signals of the first and second analog-digital converting means;
a brightness signal generating means for receiving output signals of the first arithmetic means to generate brightness signals; and
a color signal generating means for receiving output signals of the first and second arithmetic means to generate color signals by utilizing an internal color difference signal matrix.
The format of effective pixels of the first and second CCDs is based on the international standard CCIR 601 (incorporating 720 lateral pixels and 480 longitudinal pixels).
The color filter array (CFA) of the first CCD consists of horizontal repetitions of lines S1 having pixels of xe2x80x9cmagenta+cyanxe2x80x9d components, and lines S2 having pixels of xe2x80x9cgreen+cyanxe2x80x9d components.
The color filter array of the second CCD consists of horizontal repetitions of lines S1 having pixels of xe2x80x9cgreen+yellowxe2x80x9d components, and lines S2 having pixels of xe2x80x9cmagenta+yellowxe2x80x9d components.